Low-impact inertial exercise device

ABSTRACT

In one aspect of the disclosed embodiments, an inertial exercise device has an elongate member with opposing first and second end portions, and a sleeve movably coupled to the elongate member and disposed between the first and second end portions of the elongate member. A first elastic resistance element interfaces between the elongate member and the sleeve. A user-induced rhythmic movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first elastic resistance element to alternately compress and extend as the first and second end portions of the elongate member oscillate relative to the sleeve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/048,570 entitled “Low-Impact Inertial Exercise Device” and filed Mar.15, 2011, which is a continuation of U.S. patent application Ser. No.12/508,921 entitled “Low-Impact Inertial Exercise Device” and filed Jul.24, 2009, now U.S. Pat. No. 7,927,624. The contents of these priorapplications are incorporated herein in their entirety as if set forthverbatim.

FIELD

The following description relates generally to exercise equipment, andmore particularly to an inertial exercise device that can be used totone the upper body.

BACKGROUND

In-home personal exercise and weight loss equipment is an increasinglypopular field. Due to the expense of health club memberships and thetime required to travel to health clubs, many people desire to exerciseat home. However, many exercise machines are very expensive and requirea dedicated area or room for use and/or storage. For these reasons manypeople do not wish to own a large exercise machine that can exerciseseveral different muscles.

Alternatives to large home fitness machines include free weights such asdumbbells. Dumbbells have the advantage of being relatively inexpensiveand easy to use. However, one drawback of dumbbells is that they areoften very heavy and therefore can cause injury if a user excessivelystrains herself or uses poor technique. Additionally, although there aremany different dumbbell exercises, each requires a slightly differenttechnique. Many users will not be aware of all the different possibleexercise, much less the proper technique for each exercise. Accordingly,many users end up doing the same simple exercises over and over again.This results in some muscles being exercised excessively, with othermuscles being ignored completely.

Accordingly, there are needs for a home fitness device that is simpleand safe to use, that is relatively inexpensive, that does not require adedicated area for use or storage, and that effectively exercisesseveral different muscles. The embodiments of a low-impact inertialexercise device disclosed below satisfy these needs.

SUMMARY

The following simplified summary is provided in order to provide a basicunderstanding of some aspects of the claimed subject matter. Thissummary is not an extensive overview, and is not intended to identifykey/critical elements or to delineate the scope of the claimed subjectmatter. Its purpose is to present some concepts in a simplified form asa prelude to the more detailed description that is presented later.

In one aspect of the disclosed embodiments, an inertial exercise devicehas an elongate member with opposing first and second end portions, anda sleeve movably coupled to the elongate member and disposed between thefirst and second end portions of the elongate member. A first elasticresistance element interfaces between the elongate member and thesleeve. A user-induced rhythmic movement of the sleeve along theelongate member alternatively toward the opposing first and second endportions causes the first elastic resistance element to alternatelycompress and extend as the first and second end portions of the elongatemember oscillate relative to the sleeve.

The first elastic resistance element may be mounted on the elongatemember itself. The sleeve may have a first internal shoulder such thatthe first elastic resistance element is disposed between the firstinternal shoulder of the sleeve and the first end portion of theelongate member. The first internal shoulder of the sleeve may a slidebearing or formed as part of an internal bore of the sleeve. The firstelastic resistance element may be a spring, for example a helical springmounted coaxially with the elongate member and the sleeve.

The sleeve may further include a second internal shoulder opposite thefirst internal shoulder, and the exercise device may also include asecond elastic resistance element mounted on the elongate member anddisposed between the second internal shoulder and the second end portionof the elongate member. If so, the second elastic resistance elementcompresses when the first elastic resistance element extends, andextends when the first elastic resistance element compresses.

The exercise device may have a first weight attached to the first endportion of the elongate member and a second weight attached to thesecond end portion of the elongate member. A flexible boot may beattached to the sleeve and the first weight, the flexible bootenveloping the first elastic resistance element. The flexible boot, thefirst weight, and the sleeve may together form an air bellows thatexpels air through an aperture in the air bellows as the first elasticresistance element compresses in response to the user-induced rhythmicmovement of the sleeve along the elongate member. The exercise devicemay also have a second flexible boot attached to the sleeve and thesecond weight, the second flexible boot enveloping the second elasticresistance element. A central portion of the elongate member may have anexternal shoulder such that the first elastic resistance member isdisposed between the external shoulder of the elongate member and thefirst internal shoulder of the sleeve.

In another aspect of the disclosed embodiments, an inertial exercisedevice has first and second terminal masses rigidly linked together by acentral shaft, the first and second terminal masses and the centralshaft collectively having an inertia. An actuating sleeve is slidablymounted around the central shaft and has an internal bore with a firstperipheral shoulder. A first elastic resistance element is mounted onthe central shaft within the internal bore of the actuating sleeve andis disposed between the first terminal mass and the first peripheralshoulder. The first and second terminal masses and the central shaft areslidable relative to the actuating sleeve between a first position withthe first elastic resistance element compressed between the firstterminal mass and the first peripheral shoulder and a second positionwith the first elastic resistance element extended. The inertia of thefirst and second terminal masses and the central shaft causes theactuating sleeve to oscillate relative to the first and second terminalmasses and the central shaft in response to alternating rhythmic linearmotion imparted to the actuating sleeve by a user of the inertialexercise device.

The internal bore of the actuating sleeve further may also have a secondperipheral shoulder, and the inertial exercise device may also have asecond elastic resistance element mounted on the central shaft withinthe internal bore of the actuating sleeve and disposed between thesecond terminal mass and the second peripheral shoulder. If so, thesecond elastic resistance element is extended when the first and secondterminal masses and the central shaft are in the first position, and thesecond elastic resistance element is compressed between the secondterminal mass and the second peripheral shoulder when the first andsecond terminal masses and the central shaft are in the second position.

The first and second terminal masses may be disposed within the internalbore of the actuating sleeve, and the first and second peripheralshoulders of the actuating sleeve may be opposing faces of a ridge inthe internal bore of the actuating sleeve.

In yet another aspect of the present embodiments, an inertial exercisedevice has an actuating cylinder with opposing first and second ends andan internal bore. At least one mass is slidably mounted in the internalbore of the actuating cylinder. First and second elastic resistanceelements are mounted within the internal bore of the actuating cylinderand resist motion of the at least one mass toward the ends of theactuating cylinder. The at least one mass is slidable relative to theactuating cylinder between a first position with the first elasticresistance element compressed and a second position with the firstelastic resistance element extended. The inertia of the at least onemass causes the at least one mass to oscillate relative to the actuatingcylinder in response to alternating rhythmic linear motion imparted tothe actuating cylinder by a user of the inertial exercise device.

The inertial exercise device may also have a second mass rigidlyconnected to the at least one mass by a central shaft. The internal boreof the actuating cylinder may include first and second peripheralshoulders. If so, the first elastic resistance element is disposedbetween the first peripheral shoulder and the at least one mass, and thesecond elastic resistance element is disposed between the secondperipheral shoulder and the second mass. The at least one mass may havefirst and second opposing faces such that the first elastic resistanceelement is disposed between the first face of the at least one mass andthe first end of the actuating cylinder, and the second elasticresistance element is disposed between the second face of the at leastone mass and the second end of the actuating cylinder.

To the accomplishment of the foregoing and related ends, certainillustrative aspects are described herein in connection with thefollowing description and the annexed drawings. These aspects areindicative, however, of but a few of the various ways in which theprinciples of the claimed subject matter may be employed and the claimedsubject matter is intended to include all such aspects and theirequivalents. Other advantages and novel features may become apparentfrom the following detailed description when considered in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of an inertial exercisedevice.

FIG. 2 is an illustration of the inertial exercise device of FIG. 1. inuse.

FIG. 3 is an exploded view of the inertial exercise device of FIG. 1.

FIG. 4 is a cross-sectional view of one end of the inertial exercisedevice of FIG. 1 with the actuating sleeve spaced apart from a terminalmass.

FIG. 5 is a cross-sectional view of one end of the inertial exercisedevice of FIG. 1 with the actuating sleeve adjacent to a terminal mass.

FIG. 6 is a cutaway view of an alternative embodiment of an inertialexercise device.

FIG. 7 is a cross-sectional view of the inertial exercise device of FIG.6 with the actuating sleeve adjacent to a terminal mass.

FIG. 8 is a cross-sectional view of another alternative embodiment of aninertial exercise device.

FIG. 9 is a cross-sectional view of the inertial exercise device of FIG.8 with one of the elastic resistance elements compressed.

FIG. 10 is a cross-sectional view of yet another alternative embodimentof an inertial exercise device.

FIG. 11 is a cross-sectional view of the inertial exercise device ofFIG. 10 with one of the elastic resistance elements compressed.

FIG. 12 is a graph showing a comparison of total muscle activity duringa side-to-side exercise using an inertial exercise device, and astandard abdominal crunch.

FIG. 13 is a graph showing a comparison of total muscle activity duringa bicep curl with an inertial exercise device and with a standarddumbbell.

FIG. 14 is a graph showing a comparison of total muscle activity duringa triceps repetition using an inertial exercise device, and a standarddumbbell triceps extension.

DETAILED DESCRIPTION

In one aspect of the disclosed embodiments, an inertial exercise devicehas an elongate member with opposing first and second end portions, anda sleeve movably coupled to the elongate member and disposed between thefirst and second end portions of the elongate member. A first elasticresistance element interfaces between the elongate member and thesleeve. A user-induced rhythmic movement of the sleeve along theelongate member alternatively toward the opposing first and second endportions causes the first elastic resistance element to alternatelycompress and extend as the first and second end portions of the elongatemember oscillate relative to the sleeve.

FIG. 1 is an illustration of a perspective view of one embodiment of aninertial exercise device 10. In this embodiment, exercise device 10 isin the general shape of a dumbbell, having a center actuating sleeve 12and opposing terminal masses 14 that are movably coupled to actuatingsleeve 12. Flexible boots 16 extend between actuating sleeve 12 andterminal masses 14, and serve to conceal internal elements (discussedbelow) that functionally couple actuating sleeve 12 to terminal masses14. Actuating sleeve 12 is provided to enable a user to grip orotherwise hold inertial exercise device 10 with one or both hands, orwith another body part. The actual shape or contour of the actuatingsleeve 12, terminal masses 14, and flexible boots 16 may be changedaccording to design preference. Therefore, modifications or alterationsto the shape and appearance of inertial exercise device 10 may be madewithout departing from the spirit and scope of this invention. Forexample, the gripping portion 12 may be slimmer in size or contoured, ororiented transverse to longitudinal axis 18 of inertial exercise device10. Similarly, inertial exercise device 10 is not necessarily shapedlike a dumbbell and may, for example, be a straight cylindrical shaft.

Inertial exercise device 10 is devised to provide limited independentmotion of actuating sleeve 12 relative to terminal masses 14. That is,in operation, the user grips or holds actuating sleeve 12 and “shakes”inertial exercise device 10, primarily along longitudinal axis 18, asshown in FIG. 2. Since terminal masses 14 are not rigidly fixed toactuating sleeve 12, but instead are movable relative thereto, terminalmasses 14 will move out of time sync with the motion of actuating sleeve12. In other words, due to the inertia of terminal masses 14, they willinitially tend to remain at rest after the user rapidly moves actuatingsleeve 12 in one direction along longitudinal axis 18. Eventually,terminal masses 14 move in the same direction as the initial movement ofactuating sleeve 12, but the user then rapidly moves actuating sleeve 12in the opposite direction along longitudinal axis 18. Due to the inertiaof terminal masses 14, they will tend to remain in motion in the initialdirection even after the user has rapidly moved actuating sleeve 12 inthe opposite direction. Eventually, terminal masses 14 respond to thesecond movement of actuating sleeve 12 and begin to move in the oppositedirection. Thus, the user must overcome the inertia of terminal masses14 in order to rhythmically move or oscillate actuating sleeve 12 alonglongitudinal axis 18. This constant battle against the inertia ofterminal masses 14 allows the user to vigorously exercise the musclesused to move actuating sleeve 12, even if the mass of terminal masses 14is much smaller than in a traditional dumbbell.

FIG. 3 shows an exploded view of one end of inertial exercise device 10.Inertial exercise device 10 is preferably generally symmetrical so thatthe other end (not shown) of inertial exercise device 10 is ofsubstantially the same construction. Actuating sleeve 12 is slidably ortelescopically mounted on an elongate member such as central shaft 20.Thus, actuating sleeve 12 is free to slide back and forth along centralshaft 20. To support sliding motion of actuating sleeve 12 along centralshaft 20, slide bearing 24 is press fit into the internal bore ofactuating sleeve 12. Thus, in this embodiment, the internal bore ofactuating sleeve 12 does not directly contact central shaft 20, butinstead is slidably supported thereon by slide bearing 24. Slide bearing24 includes a peripheral flange or shoulder 25 which provides supportfor one end of elastic resistance element 30, which in this embodimentis a helical spring coaxially mounted on central shaft 20.

Terminal mass 14 is rigidly attached to central shaft 20 so thatterminal mass 14 cannot move relative to central shaft 20. The bulk ofterminal mass 14 is provided by annular inertial mass 52 which issandwiched between inner cap 51 and outer cap 54. Outer cap 54 includestubular protrusion 55 which receives central shaft 20. Outer cap 54 alsoincludes one or more tabs 56 which engage with openings 64 in inner cap51 when terminal mass 14 is assembled. Finally, outer cap 54 has one ormore openings 66 for receiving fasteners 57.

Support disc 53 is mounted over tubular protrusion 55 and includes oneor more threaded apertures 60. Support disc 53 serves at least twopurposes. First, it provides a support surface for the outer end ofelastic resistance element 30 so that elastic resistance element 30 maybe compressed between slide bearing 24 and support disc 53. Second,support disc 53 is used to clamp the various components of terminal mass14 together. Support disc 53 is disposed upon peripheral flange 62 ofinner cap 51 so that when fasteners 57 are inserted through openings 66of outer cap 54 and into threaded apertures 60 of support disc 53,support disc 53 clamps inner cap 51 to outer cap 54 with inertial mass52 between them.

Fastener 58 passes through tubular protrusion 55 in outer cap 54 andengages with an opening in the end of central shaft 20, thereby rigidlysecuring terminal mass 14 to central shaft 20. Finally, end cap 59 ispress-fit onto outer cap 54 in order to conceal fasteners 57. As theouter surface of inertial mass 52 may be approximately flush with theperipheral edges of inner cap 51 and outer cap 54, and end cap 59 may beapproximately flush with the outer surface of outer cap 54, terminalmass 14 can be provided with a smooth and sleek external appearance.

Also adding to the aesthetic appeal of inertial exercise device 10 areflexible boots 16 extending between each terminal mass 14 and therespective end of actuating sleeve 12. Each terminal mass 14, flexibleboot 16 and end of actuating sleeve 12 together collectively form an airbellows. As actuating sleeve 12 travels toward terminal mass 14, airenclosed by flexible boot 16 is expelled out of one or more apertures.This aperture may be in flexible boot 16 or in a portion of terminalmass 14. The air bellows thus formed serves both to make a distinctivesound of air rushing in and out of the aperture as actuating sleeve 12oscillates relative to central shaft 20, and also to partially cushioneach collision between the ends of actuating sleeve 12 and each terminalmass 14. In other words, the air bellows prevents the ends of actuatingsleeve 12 from “banging” into terminal masses 14 and making a harsh andpotentially obnoxious sound, and instead softens the collisions andmakes a “puffing” or “hissing” sound. Both the external appearance offlexible boots 16 and the rushing air sound enabled by inclusion offlexible boots 16 are aesthetically pleasing features of inertialexercise device 10. Additionally, by cushioning each collision betweenactuating sleeve 12 and terminal masses 14, wear and tear on inertialexercise device 10 is decreased.

As shown in FIGS. 4 and 5, actuating sleeve 12 of inertial exercisedevice 10 is movable between two terminal positions. In the firstterminal position, which is shown in FIGS. 4 and 5, actuating sleeve 12is at its maximum distance from first terminal mass 14 a and firstelastic resistance element 30 a is extended. In this first terminalposition, actuating sleeve 12 is also at its smallest distance fromsecond terminal mass 14 b and second elastic resistance element 30 b isfully compressed between second slide bearing 24 b and second supportdisc 53 b.

In the second terminal position, actuating sleeve 12 is at its smallestdistance from first terminal mass 14 a and first elastic resistanceelement 30 a is fully compressed between first slide bearing 24 a andfirst support disc 53 a. At the same time, actuating sleeve 12 is at itsmaximum distance from second terminal mass 14 b and second elasticresistance element 30 b is extended. Thus, the first and second terminalpositions of actuating sleeve 12 are simply inverses of one another:when actuating sleeve 12 is closest to first terminal mass 14 a (i.e.the second terminal position), first elastic resistance element 30 a iscompressed and second elastic resistance element 30 b is extended, andwhen actuating sleeve 12 is closest to second terminal mass 14 b (i.e.the first terminal position), second elastic resistance element 30 b iscompressed and first elastic resistance element 30 a is extended.Actuating sleeve 12 is slidable along central shaft 20 between thesefirst and second terminal positions.

Although elastic resistance element 30 is shown to be compressed betweenslide bearing 24 and support disc 53, numerous alternative designs areavailable. For example, slide bearing 24 may be completely eliminated sothat elastic resistance element 30 is supported by a shoulder 13 inactuating sleeve 12. This shoulder 13 is a region of the inner bore ofactuating sleeve 12 of smaller diameter than elastic resistance element30 so that elastic resistance element 30 contacts shoulder 13 andthereby resists movement of actuating sleeve 12 toward terminal mass 14.Alternatively, slide bearing 24 may be integrally formed with actuatingsleeve 12. Additionally, support disc 53 may be eliminated so thatelastic resistance element 30 is compressed against outer cap 54.Alternatively, support disc 53 may be replaced by a flange integrallyformed or otherwise attached to the end of central shaft 20.

Another embodiment of an inertial exercise device is shown in FIGS. 6and 7. In this embodiment, inertial exercise device 100 includesactuating sleeve 112 which is slidably mounted on central shaft 120.Terminal masses 114 a and 114 b are rigidly secured to the ends ofcentral shaft 120 so that actuating sleeve 112 is movable relative tocentral shaft 120 and terminal masses 114 a and 114 b. Elasticresistance elements 130 a and 130 b are mounted on central shaft 120inside internal bore 115 of actuating sleeve 112. Internal bore 115 ofactuating sleeve 112 includes first and second peripheral shoulders 113which contact the ends of elastic resistance elements 130. First andsecond peripheral shoulders 113 may be the opposing surfaces of oneridge 111 formed on internal bore 115, but may also be the surfaces oftwo separate ridges or protrusions formed on internal bore 115. In FIG.6, actuating sleeve 112 is shown in its neutral position, centeredbetween terminal masses 114 a and 114 b.

Slide bearings 124 a and 124 b are mounted on central shaft 120 andsupport sliding or telescoping movement of actuating sleeve 112 alongcentral shaft 120. Slide bearings 124 a and 124 b are fixedly secured tocentral shaft 120 so that actuating sleeve 112 moves relative to slidebearings 124 a and 124 b when inertial exercise device 100 is used bythe user. Actuating sleeve 112 therefore includes chambers 117 at bothends of inner bore 115 in order to accommodate slide bearings 124 a and124 b as actuating sleeve 112 slides back and forth along central shaft120. Thus, as actuating sleeve 112 is slid by the user away fromterminal mass 114 a and toward terminal mass 114 b, second elasticresistance element 130 b is compressed between second peripheralshoulder 113 b and second slide bearing 124 b, thereby resisting themotion of actuating sleeve 112. When actuating sleeve 112 reaches theend of its travel toward terminal mass 114 b, as shown in FIG. 7, it canbe seen that slide bearing 124 b is then at the inner end of chamber117. Similarly, when the user reverses the motion of actuating sleeve112 so that it slides toward terminal mass 114 a, first elasticresistance element 130 a is compressed between first peripheral shoulder113 a and first slide bearing 124 a, thereby resisting such motion ofactuating sleeve 112.

Inertial exercise device 100 optionally includes flexible boots 116extending between terminal masses 114 a and 114 b and each respectiveend of actuating sleeve 112. Each terminal mass 114 a and 114 b,flexible boot 116 and end of actuating sleeve 112 together collectivelyform an air bellows. The functions and features of this air bellows areanalogous to the air bellows discussed above in reference to thepreviously disclosed embodiment. As actuating sleeve 112 oscillatesrelative to central shaft 120 and terminal masses 114 a and 114 b, airenclosed by flexible boot 116 is expelled in and out of an aperture inthe air bellows. The air bellows thus formed serves both to make adistinctive sound of air rushing out of the aperture and to partiallycushion each collision between the ends of actuating sleeve 112 andterminal mass 114.

It is to be understood that other embodiments of an inertial exercisedevice are not necessarily in the shape of a traditional dumbbell. Forexample, as shown in FIGS. 8 and 9, inertial exercise device 200 is inthe shape of cylinder. Actuating sleeve or cylinder 212 is a hollowcylinder having at least one central ridge 211 forming first and secondperipheral shoulders 213. Central shaft 220 rigidly connects terminalmasses 214 to one another. Terminal masses 214 are slidably containedinside actuating sleeve 212 so that terminal masses 214 and centralshaft 220 can move in a telescopic motion from side to side insideactuating sleeve 212. This motion is resisted, however, by first andsecond elastic resistance elements 230, which are mounted on centralshaft 220 inside actuating sleeve 212. The inner end of each elasticresistance element is braced against peripheral shoulder 213.

Thus, as the user quickly moves the actuating sleeve in one directionalong its longitudinal axis 218, the inertia of terminal masses 214 andcentral shaft 220 will cause elastic resistance element 230 to becompressed between peripheral shoulder 213 and terminal mass 214. Inother words, when the user quickly accelerates actuating sleeve 212along its longitudinal axis 218, the inertia of terminal masses 214 andcentral shaft 220 will initially cause them to remain at rest relativeto actuating sleeve 212. This relative motion between actuating sleeve212 and terminal masses 214 causes one of elastic resistance elements230 to be compressed. As the user oscillates actuating sleeve 212 alongits longitudinal axis 218, each elastic resistance element isalternatively compressed in turn. FIG. 8 shows inertial exercise device200 at rest, and FIG. 9 shows inertial exercise device 200 with one ofelastic resistance elements 230 compressed after the user has quicklymoved inertial exercise device 200 along its longitudinal axis 218.Although not shown in these figures, the outer surface of actuatingsleeve 212 may include grip features such as indents or protrusions thathelp prevent inertial exercise device 200 from slipping from the user'sband.

It is to be understood that in the embodiment shown in FIGS. 8 and 9,actuating sleeve 212 may be open-ended at one or both ends. If so,terminal masses 214 may protrude partially out of the open ends ofactuating sleeve 212 as terminal masses 214 oscillate inside actuatingsleeve 212.

Another cylindrical shaped inertial exercise device is shown in FIGS. 10and 11. Inertial exercise device 300 includes actuating sleeve orcylinder 312, which is again a hollow cylinder that may have a centralridge 311 forming first and second peripheral shoulders 313. However, inthis embodiment, central ridge 311 and peripheral shoulders 313 may becompletely eliminated because, unlike the previous embodiment, they arenot needed for bracing elastic resistance elements 330. Terminal masses314 are slidably contained inside actuating sleeve 312 so that terminalmasses 314 and central shaft 320 can move in a telescopic motion fromside to side inside actuating sleeve 312. This motion is resisted,however, by first and second elastic resistance elements 330, which aremounted inside actuating sleeve 312 and disposed between terminal masses314 and the ends of actuating sleeve 312.

Thus, as the user quickly moves the actuating sleeve in one directionalong its longitudinal axis 318, the inertia of terminal masses 314 andcentral shaft 320 will cause elastic resistance elements 330 to becompressed between the ends of actuating sleeve 312 and the outer facesof terminal masses 314. In other words, when the user quicklyaccelerates actuating sleeve 312 along its longitudinal axis 318, theinertia of terminal masses 314 and central shaft 320 will initiallycause them to remain at rest relative to actuating sleeve 312. Thisrelative motion between actuating sleeve 312 and terminal masses 314causes one of elastic resistance elements 330 to be compressed. As theuser oscillates actuating sleeve 312 along its longitudinal axis 318,each elastic resistance element 330 is alternatively compressed in turn.FIG. 10 shows inertial exercise device 300 at rest, and FIG. 11 showsinertial exercise device 300 with one of elastic resistance elements 330compressed after the user has quickly moved inertial exercise device 300along its longitudinal axis 318. Although not shown in the figures, theouter surface of actuating sleeve 312 may include grip features such asindents or protrusions that help prevent inertial exercise device 300from slipping from the user's hand.

A variation of this embodiment is to use a single inertial element (i.e.mass) rather than two terminal masses rigidly connected to one another.For example, terminal masses 314 and central shaft 320 may completelyreplaced by a single cylindrical mass or slug slidably disposed inactuating sleeve 312 much like a piston. As the user oscillatesactuating sleeve 312 along its longitudinal axis 318, the slugalternately compresses each elastic resistance element 330 between itsouter face and the ends of actuating sleeve 312.

Although the embodiments disclosed above are either generally shapedlike dumbbells or cylinders, the exact shape of the inertial exercisedevice is not critical. For example, the cross-section of the actuatingsleeve and/or the terminal masses may not even be round, and may bepolygonal such as a hexagon. Further, the inertial exercise device maybe made in a wide variety of sizes, including small sizes for use withonly one hand, or larger sizes for use with both hands. For example, theinertial exercise device may be approximately 12 inches long with a 1.5inch outer diameter actuating sleeve and 3.5 inch diameter, 1.5 inchthick terminal masses. The total longitudinal travel of the actuatingsleeve relative to the central shaft and terminal masses may beapproximately 1.75 inches, or about 15% of the total length of theinertial exercise device. These dimensions are just one example of thepossible size of an inertial exercise device, and are not to beconsidered limiting in any way.

The materials used to manufacture the inertial exercise device arelikewise not critical. The actuating sleeve may be plastic and thecentral shaft may be metal, but any materials may be used. The terminalmasses generally include a metal inertial mass simply to increase theinertia of the device, but any relatively dense material may be used forthe inertial masses. The elastic resistance elements may be metal orelastomeric springs or cushions. The spring constant of the elasticresistance element is not critical but depends on the mass of theterminal masses used. For example, for 2.5 pound terminal masses, thespring constant of the elastic resistance element may be approximately10 lbs/in.

One of the main advantages of the disclosed inertial exercise devices isthat a user can vigorously exercise muscles without using heavy weights.The terminal masses used may be as small as one or two pounds each, butby quickly oscillating the device along its longitudinal axis, the useris constantly battling the inertia of the terminal masses and theresistance of the elastic resistance elements. Further, the inertialexercise device can be used to exercise far more muscles at one timethan is possible with a standard dumbbell. For example, a useroscillating the inertial exercise device along its longitudinal axis andsubstantially parallel to the user's shoulders will exercise muscles inthe arms, shoulders, chest and abdomen simultaneously.

EXAMPLE

The benefits of the disclosed inertial exercise devices weredemonstrated in a study of a total of 20 subjects (12 males, 8 females).The average age of the subjects was 25.6 years (standard deviation=4.1years) with a minimum of 21 years and a maximum of 31 years. Allsubjects were relatively healthy and relatively fit. Most participatedin some form of cardiovascular exercise program and/or strength trainingprogram.

Subjects were given a visual demonstration of the low-impact inertialexercise device (hereinafter “ShakeWeight” or “SW”). In addition,subjects were provided with approximately 5-10 minutes of practice timeusing the SW, to assure proper positioning with the device andsufficient comfort with the range of motion of the device. Oncecomfortable with the SW, subjects were fitted with electromyogram (EMG)electrodes on the following muscle sites: External Oblique (abdominal),Pectoralis Major (chest), Middle Deltoid (shoulder), Biceps Brachii(upper arm, front), Upper Trapezius and Middle Trapezius (shouldergirdle), Thoracic Erector Spinae (back), and Medial Tricep (upper arm,back). The ground electrode was placed on the anterior superior iliacspine. All EMG electrodes were placed on the right side of the body.

Subjects completed 12 different exercise routines, using the SW and adumbbell as well as performing standard crunch and push-up routines. Theroutines included the following:

1. SW bicep shake

2. SW bicep full repetition

3. SW tricep shake

4. SW tricep full repetition

5. SW push-pull

6. SW twist side-side

7. Dumbbell bicep curl

8. Dumbbell tricep extension

9. Dumbbell one-arm row (bent over)

10. Dumbbell lateral fly standing

11. Standard floor crunch

12. Standard push-up

All dumbbell routines were performed at a uniform pace of a six-secondrepetition. The pace was maintained by the use of an auditory metronomethat provided an audible beep every three seconds. Subjects wereinstructed to change direction at the sound of the beep and to maintainconstant, fluid motion. Subjects completed approximately fiverepetitions of each of the dumbbell routines and the crunch and push-uproutines. A 60-second rest was provided between routines. The SWroutines were performed for approximately six seconds for routines #1,3, 5, and 6. For routines #2 and #4 (full repetition with SW), subjectscompleted two full repetitions.

The total area of EMG (which is an estimate of muscle work), based on asingle full repetition and based on the summation of all eight muscles,was estimated for each of the twelve exercise routines. The area isbased on an established time of six seconds to complete a fullrepetition for each of the standard exercises. The same timenormalization was established for the SW exercises.

All SW routines produced significantly greater work (EMG area) comparedwith any of the standard exercises (i.e., dumbbell exercises, crunchexercise, push-up routine).

Table 1 provides the average area of EMG for each of the twelve exerciseroutines. This area is a summation of all muscles tested. For instance,the total area for the Dumbbell Curl (DB curl) was 1209.02microvolt-seconds (μv·s) and the total area for a single repetition of aShakeWeight bicep curl (SW bicep curl) was 5004.54 μv·s. The SW resultedin over four times the amount of total muscle work (summing allmuscles), compared with the standard dumbbell curl.

TABLE 1 Mean (μv · s) and standard deviation for each of the twelveexercise conditions, summed across all eight muscles. Routine Mean (μv ·s) Std. Deviation N DB curl 1209.0167 368.99781 17 DB tricep extension1214.9500 138.68263 18 DB lateral fly 1840.5500 187.83938 18 DB one-armrow  964.0500 156.60903 19 SW bicep fixed 3302.2430 535.94178 20 SWtricep fixed 2982.5200 258.56921 17 SW side-side twist 32043825383.55000 20 SW push-pull 2701.9900 505.21213 16 SW bicep curl 5004.5400789.64885 17 SW tricep extension 4307.6040 602.73946 20 Crunch  440.6333106.18907 15 Push-up 1403.0667 429.34959 18 Total 2377.4581 322.8090 205

Regardless of the exercise routine, the SW routines consistentlyresulted in significantly greater motor unit recruitment (EMG) and work(area) for each muscle, when compared to the standard exercises(p<0.05).

FIG. 12 shows comparison of total muscle activity during a side-to-sideexercise using an inertial exercise device, and a standard abdominalcrunch. The average EMG reading for all muscles was 1120 μv for theinertial exercise device side-to-side twist, and 178 μv for theabdominal crunch.

FIG. 13 shows a comparison of total muscle activity during a bicep curlwith an inertial exercise device and with a standard dumbbell. Theaverage EMG reading for all muscles was 1167 μv for the inertialexercise device bicep curl and 933 μv for the standard dumbbell bicepcurl.

FIG. 14 shows a comparison of total muscle activity during a tricepsrepetition using an inertial exercise device, and a standard dumbbelltriceps extension. The average EMG reading for all muscles was 1123 μvfor the inertial exercise device triceps repetition and 388 μv for thestandard dumbbell triceps extension.

It can thus clearly be seen that the inertial exercise device is asignificant improvement over these standard dumbbell exercises. Not onlyare more muscles exercised in each routine, but those muscles also havegreater activity.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the aforementioned embodiments, but one of ordinary skill inthe art may recognize that many further combinations and permutations ofvarious embodiments are possible. Accordingly, the described embodimentsare intended to embrace all such alterations, modifications andvariations that fall within the spirit and scope of the appended claims.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising” as “comprising”is interpreted when employed as a transitional word in a claim.

What is claimed is:
 1. An inertial exercise device, comprising: acentral shaft having an inertia; an actuating sleeve slidably mountedaround the central shaft, the actuating sleeve comprising a hand gripand an internal bore; a first mass rigidly linked together with a secondmass, with the hand grip of the actuating sleeve disposed between thefirst mass and the second mass; a first slide bearing and a second slidebearing each rigidly mounted to the actuating sleeve within the internalbore of the actuating sleeve to slidably support oscillation of theactuating sleeve relative to the central shaft; and at least one elasticresistance element mounted on the central shaft concentric with andinside the internal bore of the actuating sleeve and disposed betweenthe first slide bearing and the second slide bearing; wherein thecentral shaft is slidable relative to the actuating sleeve between afirst position with the at least one elastic resistance elementcompressed by the first slide bearing and a second position with the atleast one elastic resistance element extended; and wherein the inertiaof the central shaft causes the actuating sleeve to oscillate relativeto the central shaft in response to alternating rhythmic linear motionimparted to the actuating sleeve by a user of the inertial exercisedevice.